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While most of the headlines may be going to the European Space Agency's Rosetta probe right now - it being the first craft to enter into orbit around a comet - there are some other impressive space missions in the pipeline which shouldn't be forgotten. One of these was unveiled this week by the Japanese space agency, Jaxa - the asteroid-hunting Hayabusa-2 probe.

When Hayabusa-2 launches in November or December of this year it will begin a near-four year voyage to asteroid 1999 JU3, where it will then spend 18 months surveying the surface and running a series of experiments. By far the most audacious of these will be the "explosively-formed penetrator", which is a sciencey way of saying that missions planners are going to fire a 30cm copper ball from an on-board cannon at the asteroid's surface. The "bullet" is planned to have a relative velocity of roughly 2km/s, or around six times faster than a bullet travels when fired from a handgun - though this explanatory video from Jaxa appears somewhat lethargic by comparison:

The reason scientists want to shoot an asteroid is quite simple - dust from the crater the bullet leaves will reach escape velocity, creating a cloud of debris that Hayabusa-2 can then float through and collect samples from. (Though, just to be safe, the probe will sneak around to the other side of the asteroid in the time it takes for the bullet to reach the surface, just to avoid any debris that comes up at a dangerous speed.) Hayabusa-2 will then return to Earth by 2020, where that dust - containing, it is hoped, carbon, water and other minerals - will be studied for clues as to the nature of the early Solar System, and how life on Earth may have originated.

Besides the cannon, Hayabusa-2 will also carry four different landers. One, the Mobile Asteroid Surface Scout (Mascot), has been built by the French and German space agencies, is essentially a small laboratory in a box which will be able to take measurements of the conditions on the asteroid's surface for 16 hours after landing. Rather wonderfully, it will be able to "hop" twice using small feet before its batteries run out, tripling the positions on the asteroid's surface it can gather data from. Hayabusa-2 will also carry three Micro/Nano Experimental Robot Vehicle for Asteroid (Minerva-II) landers, more primitive rovers that should also hop languidly across the asteroid's surface, beaming back video footage to Earth and taking measurements. There's something quite beautiful about the idea of a quartet of bouncing robots exploring the surface of a tiny alien world.

In this sense Hayabusa-2 is a bigger, more ambitious version of Hayabusa-1, which only carried one Minerva rover when it arrived at the asteroid Itokawa in 2005. That mission was the first to rendezvous with an asteroid, land, collect samples and then return to Earth, but it was a mission threatened multiple times with failure. Budget cuts pushed back its launch and meant that Nasa couldn't provide it with a lander, a solar flare damaged its solar panels, internal mechanical faults threatened its ability to steer, and at several points scientists lost contact with it. It very nearly didn't have the ability to return to Earth, and, perhaps most tragically, its Minerva hopper was released at the wrong time - it missed the asteroid, floating away into space.

However, the samples that Hayabusa-1 did manage to retrieve were of immense scientific importance (once they'd been recovered from the Australian outback) - and the mission was seen as a source of national pride in Japan, becoming the subject of movies and toys. Reporting on the unveiling this week, the Japan Timesquotes mission leader Hitoshi Kuninaka as "grateful" that the new probe is finally complete, and hopeful that, this time, nothing goes wrong. “Of course, I hope things will go smoothly. We have had many difficulties in the process of developing the new asteroid probe. Space is never an easy place.”

Impactors like Hayabusa-2 are not new - Nasa's Deep Impact probe used a projectile in 2005 to stir up a cloud of debris it could then fly through and analyse - but the scale of the mission's ambition is uniquely large. It will briefly appear in the news again when it launches later this year, but the thing about probes like this - as we're seeing with Rosetta - is that they're investments which generate their own wonderful form of interest. Rosetta took ten years to reach its comet, making it almost as old as Hayabusa-1, but when it did remind of us of its lonely voyage it was with spectacular, gorgeous photographs. 2017 should hopefully bring us all another set of gifts.